The present invention relates to an apparatus and a method for the pre-breaking of city solid wastes without altering the qualities of the components thereof, treatment which precedes the separation of the different materials for the recovery of particular materials contained in the city solid wastes or the like.
Machines are already known which carry out similar operations, but they include crushing mills of a well known type, which are fitted for the treatment of the city solid wastes. These machines operate at high speed and are provided with a rotor, a statoric casing and a plurality of hammers of various configurations keyed on the rotor.
These known machines perform a volumetric reduction of the waste material and therefore also a homogenization of the components of the city solid wastes, but they do not safeguard the specific characteristics of the various materials contained in said city solid wastes. In fact, the violent mechanical action imparted by the rotor and the hammers to the materials does not only reduce the volume of the most encumbering bodies contained in the wastes without altering the smallest bodies, but on the contrary, it acts on all the materials in the same way, forming an intimate mixture thereof.
That makes difficult, and, so to say, nearly impossible, each subsequent separation of the various components for the recovery of the single materials, since on account of such violent mechanical action the various components interpenetrate with each other and are reciprocally contaminated so that they lose their original characteristics. Another inconvenience of the conventional rotating crushers consists in the fact that, due to the violent action thereof, the inner machine members are subjected to a very high wear, so that the utilization becomes nearly impossible in the practice.
There is another negative aspect of these conventional machines which is constituted of the very high energy comsuption thereof.
A last consideration against the use of the crushing mills consists in the fact that they are very expensive to produce.
The present invention provides an apparatus which overcomes the disadvantages of the conventional methods and machines and which comprises a working system including pluralities of juxtaposed blades and counterblades acting as elements of multiblade shears and which operate on the mass of the waste material carried by an endless belt conveyor preforably inclined upwards in the direction of travel, but which could be also horizontal, this belt conveyor conveying the material to be treated to pass underneath the apparatus of this invention.
The two pluralities of juxtaposed blades and counterblades operate, according to a working cycle including a forward and a return stroke, in close juxtaposed relationship to each other up to cross each with the other so as to ensure a complete breaking action on said waste material. Each blade has a considerable thickness in order to have a high strength and for the purpose of allowing the material of small size to pass through the blade and counterblade system, without being subjected to any breaking action. The volume reduction of the biggest bodies forming the waste material takes place by breaking and tearing effects, but never by a cutting action. As a result thereof, the outline or contour of the blades has not much importance and therefore it will not be necessary to maintain said outline in special conditions.
The apparatus is so designed that its two series of blades and counterblades extend through nearly the entire width of the conveyor belt, conveying the waste material and they are provided not only with shears movements, but also with up and down movements, in order that they can be able to grip therebetween the material which advances therebelow, as well as with forward and return movements in the direction of the belt travel and that is necessary in order to prevent, that during the opening phase of the blades and counterblades, these latter do not hit against the material which advances with a constant speed on the belt conveyor. This latter condition is necessary in order to prevent that the advancing material is thrown back, thus causing the formation of piles of material on the belt and giving rise to obstructions in the apparatus.
The aforementioned first two movements are obtained by means of a single hydraulic control system which, taking advantage of a linkage, is able to cause opening and closing movements of the blades and counterblades contemporaneously with up and down displacements.
Owing to the provision of the particular linkage, the blade and counterblade assembly form a rocking unit which will be called "primary hydraulic working system", in which the breaking action and the respective reaction take place entirely inside the frame carrying the blades and the frame carrying the counterblades without transmitting any stress to the carrying structure (frame) which has only the task of supporting the weight of the mechanical elements thereof.
The third movement is controlled by a second hydraulic system which will be called "auxiliary system", comprising a hydraulic cylinder, the piston of which displaces the point that could be named a fixed pivot point of the preceding "primary working system" in the direction of the conveyor belt piston which performs a forward and backward stroke.
The number of the cycles performed by the two systems, which necessarily operate according to a predetermined sequence, can be varied by simply adjusting the oil flow feeding the hydraulic cylinders according to the speed of the waste material which advances on the conveyor belt and according to the desired breaking degree.
The primary hydraulic system controlling the opening and closing movements of the blades and counterblades and their raising and lowering, can be associated with a safety means which, every time the blades and counterblades encounter a particularly too rigid body, causes automatically the reversal of the operating cycle i.e. the beginning of their return stroke so that the blades and counterblades immediately open, releasing the non-breakable object which passes beyond the blades, so that a new operating regular cycle can begin again avoiding damage to said blades and counterblades.
The series of blades consists of blades parallel to each other and aligned in the same plane, but they could be also slightly shifted to each other in order to become operative in close sequence, thus creating a progressive tearing effect of the blades which therefore requires a reduced power. In addition to this, the blades and counterblades are so shaped that their mutual crossing takes place pregressively as in the shears and not frontally. And that is provided for the purpose of reducing the stresses acting on the operating members.
From the foregoing description it results that the wear of the blades and counterblades becomes practically negligible owing to the very low number of cycles in the time unit, as well as on account of the fact that they do not perform a cutting action but only a pressure action which does not require the presence of cutting edges.
In addition to this, the required power becomes only a very small fraction of the power which is normally required when used the conventional crushing mills, on account of the fact that this machine has only the task of treating the biggest bodies, while it has substantially no effect on the waste material of small size which is only pushed forward and which constitutes the greatest percentage of the mixture of wastes.
Other objects and advantages of the invention will be apparent upon consideration of the following description taken in consideration with the accompanying drawings, in which: